This invention generally relates to the progressive die stamping art and, more particularly, to a method and apparatus for producing stamped parts which are formed utilizing a progressive die wherein carrier ribbons are not required to provide support for the stamped part as it progresses through the progressive die stamping process.
Progressive dies are among the most common type of multiple operation dies currently used in the metal stamping industry. As the name implies, a sequence of different punching, drawing, cutting, or other forming operations are performed on a continuous sheet of metal as the sheet progresses through the sequence of dies. The various operations progressively alter the original flat sheet of material until a finished part is formed and is typically separated from the sheet material by a final cut off die. Current progressive die systems generally utilize a carrier strip, carrier ribbon, or strip skeleton typically along each edge of the metal sheet to provide a structural bridge between the parts as the parts are progressively formed along the sequence of dies. The carrier ribbon is typically located along each edge of the metal sheet and is outside of the finish product area. Often, progressive die systems have encountered difficulties in achieving proper part alignment due to flexing of the material, or encounter low feed rates when utilizing a conventional carrier ribbon because the carrier ribbon is relatively fragile, particularly with light metal parts.
In an effort to overcome this difficulty, a common solution has been to increase the width of the carrier ribbons to provide a more intrinsic rigidity as the sheet presses through the progressive dies. One significant disadvantage of this approach is the increased scrap metal produced as a result of requiring the wider stock material. This disadvantage increases the cost of producing parts not only because of the increased material which must be purchased, but also because of the increased handling to remove the excess material, and if some costs are hoped to be recouped, the cost of recycling the scrap material.
Efforts have also been made to increase the rigidity of the carrier ribbons by forming a strengthening bead or rib along the edges of the sheet at an early station within the progressive die system. While incorporating the strengthening means may improve the stability of the carrier ribbon, this method simply allows for a slight reduction, if any, in the amount of scrap produced.
Currently, if a manufacturer wishes to produce a part which does not include providing the extra width required for the carrier ribbons, single action presses have been employed whereby each operation is performed with a separate die stationed on a separate press. Parts are then transferred from press to press with the operations being performed on each individual part. This approach generally involves significant labor costs and has a greater likelihood of increasing scrap rates due to misalignment of the parts within any one of the multiple dies in which the part must be oriented.
In light of the above disadvantages with the single action approach, the progressive die systems provide the advantage that there is no need to inspect the parts between operations, there is a considerable increase in safety to the operators, and only one press is needed instead of multiple presses thereby resulting in better machine utilization, less floor space, reduced die set up time and labor, and less fixed overhead costs.
With the significant advantages of utilizing a progressive die system, there is a need within the industry to provide a progressive die system which incorporates the advantages of the single action approach, specifically the elimination of any carrier ribbon required to transfer the part from station to station of the progressive die.
In accordance with the teachings of the present invention, there is provided a progressive die system allowing for a carrierless part formation and transfer from station to station as a formed part advances through a sequence of forming and/or cutting dies while maintaining structural integrity and alignment during the station to station progression.